Washington — John McCain brought an aggressive game face to the final presidential debate Wednesday night, putting his Democratic rival for the presidency, Barack Obama, on the defensive.

But in his trademark style, Senator Obama kept his cool, smiling at times as Senator McCain unloaded on him. Obama’s answers were calm and lawyerly. The Illinois senator did not hurt himself, and thus remains the odds-on favorite to win in November. His average national lead in major polls has grown to more than seven percentage points, and he is ahead in several states that voted Republican four years ago.

Still, the race is by no means over, and McCain clearly came to Hofstra University, the debate site, with some points to make. Most memorably, he announced that he was fed up with being lashed to the side of the unpopular president, George W. Bush, and made the starkest break with him yet: “Senator Obama, I am not President Bush,” he asserted. “If you wanted to run against President Bush, you should have run four years ago.”

Since launching his campaign, Obama has repeatedly stated that a President McCain would represent a third term of President Bush, pursuing what Obama likes to call the same “failed policies.” Polls show that many voters agree with that characterization. Realistically, if McCain had intended to divorce himself completely from Mr. Bush, he would have had to do it months or even years ago. Conservatives like Newt Gingrich tout French President Nicolas Sarkozy as the model for how to succeed an unpopular president from one’s own party – in his case, Jacques Chirac. The difference is that Mr. Sarkozy split from Mr. Chirac long before the French election, and succeeded in persuading voters that he would be more of a change agent than the opposition party.

If McCain goes on to lose on Nov. 4, he can rightfully blame Bush for defeating him twice – first in 2000, when McCain lost the nomination battle with the future president, and now in 2008, says Floyd Ciruli, an independent pollster based in Denver.

“McCain simply cannot plow through this with this burden,” says Mr. Ciruli.

As for who “won” the Wednesday debate, polls showed Obama coming out on top. A CBS poll of uncommitted voters scored it 53 percent to 22 percent for Obama. CNN came in at 58 percent to 31 percent for Obama. But it may be too soon to gauge whether McCain’s attacks on Obama over his past association with former '60s radical William Ayers had any effect. Voters say they don’t like negativity in candidates, but going negative can work.

By raising the subject of Mr. Ayers, which he was under pressure to do, McCain answered the call of supporters and party strategists that he should get tough with Obama on this and other controversial figures in Obama’s past, like his former pastor, the Rev. Jeremiah Wright, famous for making incendiary comments about America. Despite pleas from some strategists, McCain opted against bringing up Reverend Wright, reportedly because he does not want to risk looking racist.

But Ayers was fair game: “I don't care about an old washed-up terrorist,” McCain said. “But as Senator [Hillary Rodham] Clinton said in her debates with you, we need to know the full extent of that relationship.”

Obama came ready with a reply on Ayers, who once held a fundraiser for Obama early in his political career and who served on an educational board with Obama. Ayers is now an education professor in Chicago. Obama called Ayers’s radical acts “despicable” and noted that he, Obama, was just a boy at the time and did not know Ayers.

Obama’s ability to keep his cool under fire – and not attack back – “should certainly have an initial positive for Obama,” says Ben Voth, a forensics expert at Southern Methodist University in Dallas. “The question is whether any lingering doubts would creep in later.”

Mr. Voth also says McCain’s “base of supporters were probably satisfied that he did venture into the aggressive waters they wanted him to.”

McCain’s biggest problems are that there are fewer than three weeks until Election Day, and the nation is in a financial crisis. A bad economy is poison to the party that controls the White House, and McCain came right out of the starting gate Wednesday night aiming to show sympathy with the people – and promising action.

“Americans are hurting right now, and they’re angry,” he said, calling his fellow citizens “innocent victims of greed and excess on Wall Street as well as Washington, D.C.”

McCain then returned to a major proposal that he had laid out, with no fanfare, in the last debate, suggesting the federal government buy up shaky mortgages to stabilize the housing market. But his most memorable economic argument of the evening centered on taxes, with “Joe the plumber” as the lead character. Joe Wurzelbacher is a plumber in Toledo, Ohio, who had an extended conversation with Obama a few days ago about the senator’s plan to raise taxes on those making more than $250,000. The conversation was caught on camera, and conservatives have seized on Obama’s comment on how “when you spread the wealth around, it’s good for everybody.”

McCain repeatedly returned to “Joe the plumber” throughout the 1-1/2 hour debate, turning him into the Everyman who reaches for the American dream, only to see the government raise his taxes when he succeeds.

“Joe, I want to tell you, I'll not only help you buy that business that you worked your whole life ... and I'll keep your taxes low and I'll provide available and affordable healthcare for you and your employees,” McCain said.

Obama replied by turning the focus back to the middle class: “What I want to do is to make sure that the plumber, the nurse, the firefighter, the teacher, the young entrepreneur who doesn't yet have money, I want to give them a tax break now,” he said. “And that requires us to make some important choices.”

Joe the plumber has no doubt now joined the cast of Joes already populating the campaign – alongside the two running mates, Joe Six-Pack (aka Sarah Palin) and Joe Biden.